Intensifier-type fuel injectors are well known in the prior art. As an example, see U.S. Pat. No. 5,460,329 issued to Sturman on Oct. 24, 1995. That patent discloses an electromagnetically actuated spool valve for controlling the coupling of an effective area over an intensifier piston to an actuating or working fluid under pressure or to a vent, the intensifier piston driving a smaller piston to intensify the pressure of fuel for injection purposes. While various types of valves are known for use with such injectors, the valves generally control the flow of actuation fluid to and from the effective area over intensifier piston.
While control valves of the foregoing type can be made relatively small and fast acting, control of actuation fluid in this manner for direct fuel injection may have limitations. In particular, a diesel fuel injector may intensify fuel pressure to a pressure on the order of about 20,000 psi or higher, at which pressures the fuel will undergo substantial compression. This, in turn, means that there must be substantial actuation fluid flow into the chamber over the larger piston of the intensifier. In that regard, while, by way of an example, in an intensifier having a ratio of effective areas of 9:1, the pressure of the actuating fluid over the larger piston will only be 1/9 of the intensified pressure, the flow of actuation fluid required to achieve the compression and intensification of the fuel will be nine times that required because of the compression of the intensified fuel, thereby resulting in at least as much volumetric compression in the actuation fluid over the intensifier piston as in the intensified fuel. Consequently, intensification on actuation of the control valve(s) requires significant actuation fluid flow, and is therefore less than immediate. Also, this flow requirement sets the minimum size for the electrically operated control valves, and further requires de-intensification between injection events, making multiple injections during a single injection event difficult and energy consuming.
Known modular air and fuel controls adapted for an internal combustion engine are shown in U.S. Pat. No. 6,173,685 B1 issued to Sturman on Jan. 16, 2001 and U.S. Pat. No. 6,148,778 issued to Sturman on Nov. 21, 2000.
It is therefore desirable to provide a modular air-fuel control adapted for each engine combustion chamber that is capable of providing two stable engine valve lift (i.e., opened) positions and/or a selection of one, two or three injection pressure levels for injection fuel.
The present invention is directed to overcoming one or more of the problems as set forth above.